Peirce algebras

We present a two-sorted algebra, called aPeirce algebra, of relations and sets interacting with each other. In a Peirce algebra, sets can combine with each other as in a Boolean algebra, relations can combine with each other as in a relation algebra, and in addition we have both a set-forming operator on relations (the Peirce product of Boolean modules) and a relation-forming operator on sets (a cylindrification operation). Two applications of Peirce algebras are given. The first points out that Peirce algebras provide a natural algebraic framework for modelling certain programming constructs. The second shows that the so-calledterminological logics arising in knowledge representation have evolved a semantics best described as a calculus of relations interacting with sets.     

Visual Inspection of Multivariate Graphs

Most graph visualization techniques focus on the structure of graphs and do not offer support for dealing with node attributes and edge labels. To enable users to detect relations and patterns in terms of data associated with nodes and edges, we present a technique where this data plays a more central role. Nodes and edges are clustered based on associated data. Via direct manipulation users can interactively inspect and query the graph. Questions that can be answered include, “which edge types are activated by specific node attributes?” and, “how and from where can I reach specific types of nodes?” To validate our approach we contrast it with current practice. We also provide several examples where our method was used to study transition graphs that model real‐world systems.     

The influence of bile salts on the distribution of simvastatin in the octanol/buffer system

Abstract

Introduction: Distribution coefficient (D) is useful parameter for evaluating drugs permeability properties across biological membranes, which are of importance for drugs bioavailability. Given that bile acids are intensively studied as drug permeation-modifying and -solubilizing agents, the aim of this study was to estimate the influence of sodium salts of cholic (CA), deoxycholic (DCA) and 12-monoketocholic acids (MKC) on distribution coefficient of simvastatin (SV) (lactone [SVL] and acid form [SVA]) which is a highly lipophilic compound with extremely low water solubility and bioavailability.

Methods: LogD values of SVA and SVL with or without bile salts were measured by liquid–liquid extraction in n-octanol/buffer systems at pH 5 and 7.4. SV concentrations in aqueous phase were determined by HPLC-DAD. Chem3D Ultra program was applied for computation of physico-chemical properties of analyzed compounds and their complexes.

Results: Statistically significant decrease in both SVA and SVL logD was observed for all three studied bile salts at both selected pH. MKC exerted the most pronounced effect in the case of SVA while there were no statistically significant differences between observed bile salts for SVL. The calculated physico-chemical properties of analyzed compounds and their complexes supported experimental results.

Conclusions: Our data indicate that the addition of bile salts into the n-octanol/buffer system decreases the values of SV distribution coefficient at both studied pH values. This may be the result of the formation of hydrophilic complexes increasing the solubility of SV that could consequently impact the pharmacokinetic parameters of SV and the final drug response in patients.     

Flexible Linked Axes for multivariate data visualization

Multivariate data visualization is a classic topic, for which many solutions have been proposed, each with its own strengths and weaknesses. In standard solutions the structure of the visualization is fixed, we explore how to give the user more freedom to define visualizations. Our new approach is based on the usage of Flexible Linked Axes: The user is enabled to define a visualization by drawing and linking axes on a canvas. Each axis has an associated attribute and range, which can be adapted. Links between pairs of axes are used to show data in either scatter plot- or Parallel Coordinates Plot-style. Flexible Linked Axes enable users to define a wide variety of different visualizations. These include standard methods, such as scatter plot matrices, radar charts, and PCPs [11]; less well known approaches, such as Hyperboxes [1], TimeWheels [17], and many-to-many relational parallel coordinate displays [14]; and also custom visualizations, consisting of combinations of scatter plots and PCPs. Furthermore, our method allows users to define composite visualizations that automatically support brushing and linking. We have discussed our approach with ten prospective users, who found the concept easy to understand and highly promising.     

Learning at work - a combination of experience based learning and theoretical education

Training and learning at work is important as employees competence has to meet organisational requirements for flexibility. This study examines conditions and obstacles in integrating a web-based course at work in order to enhance employees level of competence. Employees view of working condition, competence and how they learn at work is also of importance. A selection of 35 people was made at a company which is part of a large business. The design was quantitative with complementary qualitative data. The employees had a positive attitude towards work despite increasing difficulties in work tasks and an increasing workload, which was the greatest barrier of integrating the web-based course at work. Competence development involved a certain degree of stress, but was outweighed by the fact that it was stimulating and led to the work feeling easier. To manage work, knowledge was obtained primarily by colleagues and company courses.     

The effects of glossy screens on the acceptance of flat‐panel displays

Abstract— The TCO requirements provide well‐known and recognized quality labels for displays. For these requirements to remain useful, they must continuously be reviewed and updated when necessary. The study described here was performed in response to the market trend of designing flat‐panel displays and notebooks with glare panels. The purpose of this study was to investigate subjective responses to display screens of different gloss levels for office workers working on different tasks under normal office‐lighting conditions. The study consisted of three parts, one where the users should set an acceptable reflex level, one where the user should rate their disturbance on a category scale, and one where the visual acuity of the users were investigated whether they were affected by glare or not. The results show that increasing gloss and increasing luminance levels had negative effects on the acceptance and the disturbance of reflexes. There were statistically significant differences in the acceptance and the disturbance levels between screens with low gloss and screens with high gloss, which suggests that screens with the highest gloss levels should be avoided. The study did not show an effect on the performance based on acuity testing.     

Computing multiscale curve and surface skeletons of genus 0 shapes using a global importance measure

We present a practical algorithm for computing robust, multiscale curve and surface skeletons of 3D objects. Based on a model which follows an advection principle, we assign to each point on the skeleton a part of the object surface, called the collapse. The size of the collapse is used as a uniform importance measure for the curve and surface skeleton, so that both can be simplified by imposing a single threshold on this intuitive measure. The simplified skeletons are connected by default, without special precautions, due to the monotonicity of the importance measure. The skeletons possess additional desirable properties: They are centered, robust to noise, hierarchical, and provide a natural skeleton-to-boundary mapping. We present a voxel-based algorithm that is straightforward to implement and simple to use. We illustrate our method on several realistic 3D objects.     

Views on visualization

The field of visualization is maturing. Many problems have been solved and new directions are sought. In order to make good choices, an understanding of the purpose and meaning of visualization is needed. In this paper, visualization is considered from multiple points of view. First, a technological viewpoint is adopted, where the value of visualization is measured based on effectiveness and efficiency. An economic model of visualization is presented and benefits and costs are established. Next, consequences and limitations of visualization are discussed (including the use of alternative methods, high initial costs, subjectiveness, and the role of interaction). Example uses of the model for the judgment of existing classes of methods are given to understand why they are or are not used in practice. However, such an economic view is too restrictive. Alternative views on visualization are presented and discussed: visualization as an art, visualization as design and, finally, visualization as a scientific discipline.     

A comparative study of direct and indirect evaluation of piezoelectric properties of electrophoreticaly deposited (Ba,Ca) (Zr,Ti)O3 lead-free piezoceramics

The development and optimisation of piezoceramics are targeted usually to enhance their piezoelectric properties evaluated by both the direct or indirect measurement methods. The presented work aims to elaborate on the correlation of one direct (Berlincourt) and two indirect (convert and field-dependent) piezoelectric measurement methods on various material states. The role of the ceramic powder treatment by ball milling and electrophoretic deposition (EPD) technique on the determined electric properties as well as basic physical and mechanical properties of (Ba_0.85Ca_0.15) (Zr_0.1Ti_0.9)O₃ ceramics (BCZT) was investigated. It was found that the EPD technologically supported by milling allows obtaining thick and dense deposits (>2 mm). After sintering, the BCZT ceramics with a relative density of >95%, hardness in the range of 2.3–2.9 GPa and piezoelectric coefficients of d₃₃* = 940 pm/V, d_33(E=0) = 427 pm/V and d₃₃ = 364 pC/N can be achieved. Reported results also suggest that indirect (field-dependent) and direct (Berlincourt) measurements of the piezoelectric coefficients can be comparable at optimal poling conditions.